Over the years, a broad range of research has confirmed that omega-3 fatty acids found in fatty fish like salmon, tuna and sardines promote heart and brain health. Now researchers at the University of Pennsylvania’s Perelman School of Medicine have found that taking fish oil supplements isn’t as effective at keeping blood pressure under control as eating an actual fish.

The animal study published in the U.S. Proceedings of the National Academy of Sciences shows that eating oily fish helped open ion channels, a complex series of membranes in the cells that line blood vessels, letting sodium, calcium and potassium in and out of those crucial cells and helping reduce blood pressure. Because fish oil supplements did not activate the ion channels, they didn’t reduce blood pressure in the same way.